This application claims the priority of German patent document 100 00 535.7, filed Jan. 8, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method of calibrating a rollover sensor for a vehicle.
In such rollover sensors, acceleration sensors which can determine the alignment of a vehicle in space (particularly in the three space axes) are generally used to detect rollover events. A problem of using more favorably produced sensors is their fluctuation around the zero position, which is mainly caused by temperature effects.
It is an object of the invention to provide a method by which an initially mentioned rollover sensor can be calibrated in a simple manner.
This and other objects and advantages are achieved by the method according to the invention, in which the inclination reported by a rollover sensor is continuously averaged along a defined route in at least one axis. By means of such averaging along a covered route, any drift is canceled out. The average value will then correspond to the zero position. Preferably inclination measurements and assigned averaging take place in all three space axes.
For inclinations about the longitudinal axis, the above-selected method will be sufficient. In the case of inclinations about the transverse axis, however, it may occur that during extended uphill or downhill drives, as a result of the average inclination of the road, errors occur which are caused by the averaging process.
To avoid this effect, in a particularly preferred embodiment, the average inclination is determined along a defined route from the air pressure change along this route. More precisely, the absolute air pressure can be determined by means of an air pressure sensor and, from the barometric altitude formula, the altitude of the vehicle above sea level can be determined. As a result, a change of altitude can be determined in a simple manner along a defined route. In this case, weather-caused air pressure fluctuations are averaged out. By means of the quotient of the altitude change with respect to the defined driving route, the average inclination can be computed along this route, and used to correct the determined, averaged inclination in the driving direction.
In many vehicles, pressure sensors are already used in the door area for detecting lateral collisions. In the future, the electronic system of the engine will also have an air pressure sensor for taking into account the influence of the ambient air pressure on the power of the engine. By using these existing air pressure sensors for the present invention, the use of additional hardware components is avoided.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.